Make sure you have the right OS and Oracle patches when using dynamic SGA features (9i+)

Dynamic SGA utilizes an operating system functionality known as Dynamic Intimate Shared Memory (DISM). This is a fairly new creature and may not be fully mature on all platforms. The general idea is that memory segments can be locked and unlocked from within the OS kernel as is required by the application, the Oracle RDBMS in this case. If the OS isn't up to the current patch levels and properly tuned, a wide variety of problems can occur, including performance degradation.

Enabling dynamic resizing by setting the SGA_MAX_SIZE instance parameter spawns an additional Oracle background process. If this process isn't running with proper permissions or should die, further problems could ensue. Oracle 10g includes features to help stabilize this feature, but Release 1 of Oracle 9i could present more problems than the feature is worth. Before setting SGA_MAX_SIZE, make sure you upgrade to Release 2 of 9i. You're also strongly advised to consult with your friendly neighborhood system administrator before proceeding.